Process for extracting ores and the like



A. C. VAN ES PRocEss FOR EXTRACTING oREs AND THE LIKE Aug. s, 1939.

Filed Nov. 5, 1938 f7 Vgn @s v M Patented Aug. 8, 1939 4UNITED STATES PATENT AolFFlcr.

Adriaan Cornelis van Es, Huizen, Netherlands,

assigner to N. V. Maatschappi;| Voor Zwavelzuurbereiding Voorheen G. T. Ketjen & Co., Amsterdam, Netherlands Application November 3, 1938, Serial No. 238,671

In the Netherlands December 24, 1935 The process relates to extracting ores and the like and more particularly to recovering copper and cobalt from oxide ores, including silicates and roasted sulphides.

The application is a continuation in part of `the application Serial Number 118,685', led Dec. 31, 1936, for Process for extracting ores and the like. My prior application describes and claims a method of extracting'metals (specifically nickel) having a lower heat of combustion than iron from their oxide, silicate and roasted sulfide ores, wherein such an ore is heated in v the presence of a reducing gas containing steam under conditions producing the reductionvof said metals, while iron and metals having a higher heat of combustion than iron are retained in the oxidized state, and thereafter recovering the soreduced metals. My present application is directed/to the use of the same general process in recovering metals selected from a group consisting of copper and cobalt from ores of the general character described.

In order to obtain the desired metals the raw material must be made extractable. According `to the present process this is effected by the application of short-circuited element-couples in the mass which has to be extracted, from4 which local cells are formed by subsequently adding extraction electrolytes. Hereby care has to be taken that the metal to be obtained. forms the most electronegative electrode of. the couple and `that a more electronegative undesired element is not present in the metallic form.

It is necessary that vthe local cells are accessible for-.the extraction electrolyte. This may be attained in an appropriate manner by bringing the `ore after being made extracta'ble into an extraction electrolyte in a more or. less nely ground condition. The penetration of the electrolyteinto the 4interior of each individual local cell maybeincreased by changing the pressure, the temperature and the surface tension.

In order to be able to form in the'mass to be extracted thef-metal-couple in which the desired metal ,isgthe most lelectronegative one, it is necessary that a more'electropositive element is present in the mass."

ffrii'tfbyfrimary eens it is known that the amount If such element should not be present it may be formedv from`jconstituents of the 'mass or it of the current delivered is considerably increased by the presence of a depolarizer in such a cell,

techniques of the generation of cur-'1 extraction operation. If for instance it is desired to extract nickel, ferrie oxide may be 'used as such.

If the raw material is an ore one of the con.

stituents of this ore may be used as a depolarizer or converted into it. In another case it will be necessary to introduce the constituents, from which a suitable depolarizer may be formed from outside into the ore. The place ofthe depolarizer is in the vicinity of the most electronegative element. 'Ihe depolarizer will retain a favourable action on the extractiononly` if the access of the electrolyte to this most electronegative element is not hindered by too large an extent of the depolarizer. Also a depolarizer may be used in the dissolved state, e. g. cupric salts or cobalti salts.

With regard to a certain electrolyte the metals are ranged in a distinct electromotive tension series.

Premising that in the mass to be extracted these metals are converted into the metallic form the logical consequence will be that for one and the same electrolyte 'they would be obtained following that series and that also undesired metals would be obtained.

By application of another electrolyte by which another sequence in the E. M. F. series is caused, the undesired metal being the more electropositiv'e does not dissolve.

Applicant has found the following `Ways of preventing the dissolving of an undesired metal:

(a) From the undesired metal a compoundfbeing insoluble in the electrolyte is formed before adding the electrolyte. Ihis may be carried out by reducing the oxide ores and the like with a suitable mixture of reducing gas and steam at a temperature of at least 400 C. V

` (b) By choice of a certain electrolyte, causing the undesired metal even if it be present in the metallic state to form compounds insoluble in that electrolyte, whereas the desired metal does form soluble compounds.

Example 1.--A sulphide copper'ore from Tasikfmalaya, Java, having approximately thefollowingconiposition: S 27, Cu 5,. 5, Te.26, vSiOz 36, was subjectedto an oxidizing roasting.

' a. Part of the so oxidized ore was reduced during about 2 hours at 700 C. with a reducing gas consisting of parts by volume `of"il1uminating gas andv 70 parts of steam. Then the supply of steam was shut oi and the so reduced ore cooled down in an atmosphere of illuminating gas.

b. Another part of the roasted ore was reduced at 700 C. with illuminating gas and subsequently cooled in an atmosphere of illuminating The copper content of a was 6.4%.

'I'he copper content of b was 6.6%.

50 grams of va. were extracted with 1280 c. c. of 0.20 N. sulphuric acid. After 12 hours of stirring and of aerating the solution contained 2.76 gr. ofI copper equal to 86.2%.

50 grams of b were extracted in exactly the Same way. After 12 hours of stirring and of aerating no copper at all could be found in the solution.

In case a the local cells copper-carbon are formed, whereas the iron is brought into an insoluble oxide form.

Indcase b the local cells copper-carbon as well as iron-carbon are formed, the local cell "iron-carbon having an electrical tension of 1.4

volt at pH=1 and of 1.8 volt at pH=14, the local cell copper-carbon" having an electrical tension oi' 0.65 volt at pH=1 and of 1.35,volt at pH=14.

Therefore in case b iron goes into solution be- 'Iore copper, consuming the available sulfuric acid, leaving no extraction electrolyte for cop- Per extraction.

Example 2.-A Rhodeslan oxide copper ore, containing 2.8% of copper, 12% of iron, 60% of silica was ground to a grain size of 1 millimeter.

I., Part of this was reduced at a reduction temperature of 700 C. with a mixture oi illuminating gas and steam to the proportion of 80 volume Darts of illuminating gas and 225 volume parts of steam, cooled to 200 C., the steam supply shut ott and cooled to room temperature in an atmosphere of illuminating gas.

II. Another part was reduced without the addition of steam at the same temperature.

DI. A third part was reduced without the addition of steam, however at a. lower temperature (about 350 C.). Extraction was carried out by percolating 40 grams of the reduced ore` with a solution containing:

d, Cubic centimeters Saturated ammonium carbonate solution---" 20 Ammonia 25% 20 water 2o.

The height of the ore layer amounted to 'centimeters.

In the rst case (partI) 97.3%A of the copper could be extracted in 6 hours of percolation.

In the sec'ond case (part II) no copperat all could be extracted in 6 hours of percolation.

In the third case (part III) only 4.3% of the copper could be extracted in 6 hours of percolation.

In the second and third case, iron wentinto solution in the ferrous form and was' afterwards precipitated in the ferrie form. l 'I The solutions became highly contaminated with iron which precipitated in the ore layer and caused the 'layer to-become clogged preventing percolation in the second case and hindering percolation inithe third case (layers of 20 c. m. of

height),

Increasing the increases the troubles from clogging' the layers with ferrie' hydroxide in the second and third case. With aheight ot 4 -metersin the met case troubles were encountered.v In the second height of the f percolation layer case with a height of 20 centimeters only the percolation became impossible within two hours` because the layer was absolutely clogged.

In the third case with a height of l meter percolation became impossible after three hours.

If percolating with cupric ammonium carbonate solution the same diiliculties arise in the second and third case. In the first caseno troubles by clogging were encountered because n'o iron could go into lthe solution and precipitate therefrom.

Example 3.--A Rhodesian oxide and silicate copper ore, containing copper 4.01, iron 3.41, alumina 2.64, silica 63.27, calcium oxide 6.1, magnesium oxide 5.75 and loss by calcination 13.6, was ground to a grain size of l mm. calcium and magnesium were present as carbonates. In order not to decompose these carbonates a reduction temperature of 450 C. was chosen and a mixture of gas and steam to the proportion of 75 volume parts of illuminating gas and 220 volume parts of steam.

The reduction time was 45 minutes, after which .the reduced ore was cooled to 200 C., the steam supply shut oi and cooled to room temperature in an atmosphere of illuminating gas.

Extraction was carried out by percolating the reduced and cooled ore with a solution, containing ammonia, ammonium-carbonate and water. In 6 hours of extraction time 98% of the copper could be dissolved. If reducing another part of the ground ore at the reduction temperature of 450 C. without the addition of steam to the re. duction gas, troubles from clogging with ferrichydroxide -were encountered. After 3 hours of percolation through a layer of 2 meters of height the rate of flow was very low and after 4 hours it stopped entirely. Only 14% of the copper was found in the solution. l

If reducing a third wart of the ground copper at a temperature of 650 C. in a mixture of gas and steam to the proportions of 73 parts of illuminating gas and 245 parts of steam the troubles encountered were not due to iron, but to a hydraulic binding of the decomposed calcium. magnesium carbonate with the aid of the carbondioxide content of the extraction-solution, which meant an uneconomic consumption oi the ammonium carbonate as well as hindering of proper entrance of the. leaching solution into the local cells copper-carbon.

Therefore the reduction temperature ci 450 C. and the gas steam mixture 75:220 were chosen.

'Ihe composition of `the illuminating gas of Examples 1, 2 and 3 was: CO2 3, hydrocarbons 3, O2 1,'CO 18.4, H2 46.5, CH; 16.5, N2 10.

Example 4.--The Rhodesian copper ore as described in/Example 2 was ground to a grain size of 1v mm.

The ore was reduced at a reduction temperature of 680 C. with a mixture ofgenerator-gas .and 'steam to the proportion of 1 volume part of gas and 1 volume part of steam, cooled to 180 C., the steam supply shut of! and cooled to room temperature in an atmosphere of generator-gas.

On leaching by percolating with a solution of ammonia, ammonium-carbonate and water 96% of the copper was dissolved in 7 hours. l The composition of the gas was: CO: 4, CO 26, Hz 13,

ture of 450C. with a mixture of coke furnace gasand steam to the proportion ot 82 volume Il of the gas and 230 volume parts of steam cooled' to 210 C., the steam supply shut off and cooled to room temperaturein an atmosphere of coke furnace gas.

Extraction was carried out by percolating wit a solution o f ammonia, ammonium carbonate and water. In 6 hours 97.6% of the copper was disf solved. The composition of the gas was: CO2 1.2, hydrocarbons 1.6, O2 0.4, CO 5.9, H2 63.5, CII4 23.9, N2 3.5. i

Example 6.-A sulphide cobalt ore was ground to pass 30 mesh sieve, then roasted'and after roasting reground to pass 30 mesh sieve. The composition after roasting was: iron and alumina 42.4, silica 30.5, sulphur 0.60, copper 0.94, cobalt 1.5.

I. Part of the roasted and ground ore was reduced at a temperature of '700 C. with a mixture of illuminating gas and steam to the proportion of 70 parts by volume vof illuminating gas and 84 parts by volume of steam during one hour and a half. The steamv supply was shut olf and the reduced ore cooled in an atmosphere of illuminating gas.

'Iheso reduced and cooled ore was extracted with a 0.02 N. sulphuric acid solution which was aerated during the extraction.

After 5 hours 78% of the cobalt wasfourid` in the solution together with 83% of the copper. The amount of sulphuric acid was equivalent to twice copper-|-cobalt.4

reduced at 680' C. with a mixture of illuminating gas and steam to the proportion 50 parts by volume of illuminating gas and 115 parts by volume of steam and cooled to 450 C. in the atmosphere of this gas-steam mixture. The steam supply Was shut off and the reduced ore cooled to room temperature in an atmosphere of illuminating gas. Y

Thereduce'd ore was extracted with a solution containing ammonia, ammonium-carbonate and water by stirring the ore with said solution and aerating the solution.

After 9 hours of extraction 91% of the copper and '72% of the cobalt were found in the solution.y

` The composition of the illuminating gas in the three cases of Example 4 was: CO2 2.8, hydrocarbons 3.1, oxygen 0.2, CO 18.2, H2 47.1, CH4 15.9,

The reduction as described may be carried out in a long revolving drum furnace.. Theore is reduced at the chimney end of this furnace. At the ore discharging end gas is introduced which moves countercurrent to the ore. At some distance from the gas inlet, so nearer to the chimney end steam isI blown into the furnace. Y Still l nearer to the chimneyend air may be introduced into the furnaceiby which the combustion of the residual gas and at the same time heating of the ore to 700 C. is obtained.

A furnace of this kind is represented in the drawing showing a pilot plant furnace.

In this drawing, which only is to be taken 'by Way of illustration, and not as a limitation,

A designates a rotary kiln, mounted and rotated in conventional manner. This kiln is functionally divided into reduction Zones 6 and 1, heated from outside, and cooling zone 8. The upper portion of the cooling zone is lagged with non-conducting material to conserve the heat, while the.`

lower end is free from lagging to facilitate rapid cooling.

B designates'a feeding devicelwhich comprises a feedingv screw C, whose axis is `tubular and is rotated by pulley I0.

Within this tubular axis, a pipe for conveying steam into the kiln is located, which pipe assumes a spiral form 4 inside the kiln and ends at or near the upper end of the cooling zone.-

The lower end of the kiln is closed, and the upper end is furnished with means for excluding air as shown.

Between the two heating zones, means designated by the numeral 9, for the introduction of air, are located. 'I'hese means are shown simply as apertures in the wall of the kiln but would be constructed with conventional regulating means in actual practice.

The lower end of the kiln has `a discharge device which is shown as a conduit passing around a maj or portion of its exterior and which opens into the kiln at one end and into the atmosphere at the other end. By this device the ore always lls a portion ofthe conduit and excludes air from the kiln.

In 'operation the kiln is set in rotation, the heating zones are heated to the proper temperature, and the ore fed therein.

Steam is passed into the kiln through pipe 4, and reducing gas'at its lower end, and if desired, air may be introduced between the two heating zones.

The reducing gas meets the descending ore and passes out ofthe kiln through apertures 5 at its vupper end. v

Means for controlling the amount of steam, air and reducing gas areof conventional form and are not shown.

Iclaim:

l. The process of extracting metals selected from a group consisting of copper and cobalt from their oxide, silicate and roasted sulfide ores which comprises heating such an ore with a reducing gas containing steam at such temperatures and for such time that only the said metals are reduced to the metallic state while iron and metals having a higher heat of combustion than iron are retained in the oxidized state and recovering the so-reduced metals from the product.

2. The process of claim 1 wherein the ore is heated lfor at least 20 minutesI at temperatures above-400 C.-

3. The process of claim 1 wherein the reduced ore is cooled in a; reducing atmosphere prior to recovery of the metals. v

4. The process of claim 1 wherein the reduced ore is cooled in an atmosphere of a reducing gas selected from a class constisting of carbon 'monoxide and hydrocarbons for at least 15 minutes prior to recoveryof the metals.

' 5. The process of claim 1 wherein the reduce metals are recovered by extraction with an electrolyte.

6. The process of claim 1 wherein the reduced metals are recovered by extraction with an electrolyteand atmospheric oxygen.

7. 'I'he process of claim 1 wherein the ore treated is a copper ore and copper is recovered ed is a cobalt ore and cobalt is recovered there-- from.

9. The process of extracting metal selected from a group consisting of copper and cobalt from their oxide, silicate and roasted sulde ores which comprises subjecting such an ore for at least 20 minutes at a temperature of at least 400 C. to

ythe action of a reducing gas containing steam in such an amount that said metals are reduced to the metallic state while iron and metal having a higher heat of combustion than iron are retained in. an oxidized state, then cooling the so-reduced ore for at least 15v minutes in the presence of a reducing gas comprising carbon monoxide and hydrocarbons and then treating the reduced and cooled ore with an extraction electrolyte and atmospheric oxygen. I

ADRIAAN CORNELIS VAN ES. 

